Sahih Bukhari | Volume 1 | Hadith Number 702

My father said, "Allah's Apostle used to raise both his hands up to the level of his shoulders when opening the prayer; and on saying the Takbir for bowing. And on raising his head from bowing he used to do the same and then say "Sami a-l-lahu Liman hamida, Rabbana walaka-l-hamd." And he did not do that (i.e. raising his hands) in prostrations.